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The most important tubes ever made.....



 
 
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  #11  
Old February 4th 19, 12:55 AM posted to rec.audio.tubes
Big Bad Bob
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Posts: 348
Default The most important tubes ever made.....

On 02/02/19 17:26, wrote:
> Big Bad Bob wrote:
>
>>
>>
>> And of course a guitar amp is probably going to be designed to pass a
>> more limited frequency range. You can see that when you look at
>> replacement output transformers, typically rated for 100Hz to maybe 4kHz
>> as opposed to a 20Hz-20kHz range for hifi/stereo amplifiers.
>>

>
> ** The output transformers used in tube guitar amps are normally a lot better than you suggest.
>
> Eg: A Marshall 50W output transformer has its upper -3dB point at 45kHz.
>
> The small signal, low frequency response is -3dB at 1Hz (yes, one Hertz) but core saturation at rated power becomes dominant below about 5OHz.
>
> IME most output transformers used in brand name amps have similar specs.


hmmm, that goes against what I've read over on 'amplifiedparts.com' for
'original replacement' transformers, as opposed to the ones made by
Hammond (which are nearly always better).

the DC blocking capacitors in guitar amps _are_ de-rated a bit over what
you'd see in a hi fi system, last I went through one. Tone controls are
also a little strange compared to hi fi equivalents. But it's part of
"the sound" [and also costs less, which I think is what drove it].
Ads
  #12  
Old February 4th 19, 01:17 AM posted to rec.audio.tubes
Phil Allison[_4_]
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Posts: 457
Default The most important tubes ever made.....

Big Bad Bob wrote:

> >
> >>
> >> And of course a guitar amp is probably going to be designed to pass a
> >> more limited frequency range. You can see that when you look at
> >> replacement output transformers, typically rated for 100Hz to maybe 4kHz
> >> as opposed to a 20Hz-20kHz range for hifi/stereo amplifiers.
> >>

> >
> > ** The output transformers used in tube guitar amps are normally a lot better than you suggest.
> >
> > Eg: A Marshall 50W output transformer has its upper -3dB point at 45kHz.
> >
> > The small signal, low frequency response is -3dB at 1Hz (yes, one Hertz) but core saturation at rated power becomes dominant below about 5OHz.
> >
> > IME most output transformers used in brand name amps have similar specs.

>
>
> hmmm, that goes against what I've read over on 'amplifiedparts.com' for
> 'original replacement' transformers, as opposed to the ones made by
> Hammond (which are nearly always better).
>


** Never rely on " information " posted on web sites written by musicians and storekeepers.



> the DC blocking capacitors in guitar amps _are_ de-rated a bit over what
> you'd see in a hi fi system, last I went through one. Tone controls are
> also a little strange compared to hi fi equivalents. But it's part of
> "the sound" [and also costs less, which I think is what drove it].




** Guitar amps have many differences from " hi-fi" amps, the most significant of which a

1. Low or no negative feedback around the output stage, so THD is relatively high at 2 to 5% below clipping.

2. Low class AB bias, so full power operation is mainly class B exaggerating point 1.

3. High output impedance, due mainly to point 1.

4. Non flat response from the tone circuits ( typically the treble end is boosted ) and deliberate distortion incorporated in same.

Of course, the speakers fitted to combo amps have limited response, 70 to 4kHz with a presence peak around 2 to 3 KHz being typical.

But they ARE damn efficient, up to 105dB/watt for some 12 inch models.


..... Phil

  #13  
Old February 4th 19, 09:35 AM posted to rec.audio.tubes
Don Pearce[_3_]
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Posts: 2,269
Default The most important tubes ever made.....

On Sun, 3 Feb 2019 16:17:27 -0800 (PST), Phil Allison
> wrote:

>Big Bad Bob wrote:
>
>> >
>> >>
>> >> And of course a guitar amp is probably going to be designed to pass a
>> >> more limited frequency range. You can see that when you look at
>> >> replacement output transformers, typically rated for 100Hz to maybe 4kHz
>> >> as opposed to a 20Hz-20kHz range for hifi/stereo amplifiers.
>> >>
>> >
>> > ** The output transformers used in tube guitar amps are normally a lot better than you suggest.
>> >
>> > Eg: A Marshall 50W output transformer has its upper -3dB point at 45kHz.
>> >
>> > The small signal, low frequency response is -3dB at 1Hz (yes, one Hertz) but core saturation at rated power becomes dominant below about 5OHz.
>> >
>> > IME most output transformers used in brand name amps have similar specs.

>>
>>
>> hmmm, that goes against what I've read over on 'amplifiedparts.com' for
>> 'original replacement' transformers, as opposed to the ones made by
>> Hammond (which are nearly always better).
>>

>
> ** Never rely on " information " posted on web sites written by musicians and storekeepers.
>
>
>
>> the DC blocking capacitors in guitar amps _are_ de-rated a bit over what
>> you'd see in a hi fi system, last I went through one. Tone controls are
>> also a little strange compared to hi fi equivalents. But it's part of
>> "the sound" [and also costs less, which I think is what drove it].

>
>
>
>** Guitar amps have many differences from " hi-fi" amps, the most significant of which a
>
>1. Low or no negative feedback around the output stage, so THD is relatively high at 2 to 5% below clipping.
>
>2. Low class AB bias, so full power operation is mainly class B exaggerating point 1.
>
>3. High output impedance, due mainly to point 1.
>
>4. Non flat response from the tone circuits ( typically the treble end is boosted ) and deliberate distortion incorporated in same.
>
>Of course, the speakers fitted to combo amps have limited response, 70 to 4kHz with a presence peak around 2 to 3 KHz being typical.
>
>But they ARE damn efficient, up to 105dB/watt for some 12 inch models.
>
>
>.... Phil


This is all vital stuff. You must consider that a guitar amplifier is
not a reproduction device. It is an integral part of the instrument,
and confers a large amount of the sound of the instrument. Flat
response and low distortion are the last things a guitar amplifier
designer is looking for.

d
  #14  
Old February 5th 19, 10:19 AM posted to rec.audio.tubes
Big Bad Bob
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Posts: 348
Default The most important tubes ever made.....

On 02/04/19 00:35, Don Pearce wrote:
> On Sun, 3 Feb 2019 16:17:27 -0800 (PST), Phil Allison
> > wrote:
>> Of course, the speakers fitted to combo amps have limited response, 70 to 4kHz with a presence peak around 2 to 3 KHz being typical.
>>
>> But they ARE damn efficient, up to 105dB/watt for some 12 inch models.
>>
>>
>> .... Phil

>
> This is all vital stuff. You must consider that a guitar amplifier is
> not a reproduction device. It is an integral part of the instrument,
> and confers a large amount of the sound of the instrument. Flat
> response and low distortion are the last things a guitar amplifier
> designer is looking for.


right, a slightly different way of saying what I did earlier, about the
amplifier being part of "the sound". So then it also matters who made
the tubes, among other things, as they are part of "the sound" as well.

 




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